It really amazes me how the Grease Pencil has grown in the past year or two. When i first came to blender for serious about 6 years ago, I found the grease pencil to be a great tool as an animation helper, you could create your thumbnails there, and i used it a lot to draw paths for my arcs when doing animation.
Now it’s almost a full fledged 2D animation suite, check out what the guys over at pepeland are doing:
The Adventures of LollypopMan 